In recent years, various fuel cell devices storing a cell stack device obtained by electrically connecting a plurality of solid oxide fuel cells in series in a storage container have been proposed as the next-generation energy.
The solid oxide fuel cells of such a fuel cell device have a pair of flat surfaces in parallel to each other, a fuel gas passage for circulating fuel gas inside, and a conductive support member containing Ni. A solid oxide fuel cell has been proposed in which a fuel electrode layer, a solid electrolyte layer, and an oxygen electrode layer are successively laminated on the one flat surface of the conductive support member and an interconnector layer is laminated on the other flat surface (for example, Japanese Unexamined Patent Application Publication No. 2008-84716).
Heretofore, the solid oxide fuel cell has been configured so that a solid electrolyte layer containing a ZrO2-based dense sintered compact formed in such a manner as to surround the circumference of a conductive support member and an interconnector layer containing a LaCrO3-based dense sintered compact are joined to each other in such a manner that both ends of the solid electrolyte layer are overlapped with both ends of the solid electrolyte layer.
More specifically, it has been configured so that the circumference of the conductive support member is airtightly surrounded by the solid electrolyte layer and the interconnector layer to prevent fuel gas which passes through the inside of the conductive support member from leaking to the outside from a dense cylindrical body formed by the solid electrolyte layer and the interconnector layer. Therefore, the relative density of the solid electrolyte layer has been set to 97% or more and a denser film has been demanded.
A fuel cell has also been developed in which a solid electrolyte layer contains a dense electrolyte layer disposed on the side of a fuel electrode layer and a porous electrolyte layer disposed on the side of an air electrode and the porosity of the dense electrolyte layer is 5% or less and the porosity of the porous electrolyte layer is 20 to 60% (for example, Japanese Unexamined Patent Application Publication No. 2009-259746).
The following is a list of the aforementioned background art:
    Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2008-84716    Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2009-259746